Ex-Tesla engineer Doug Field is back at Apple, working on its self-driving-car program, Project Titan

Doug Field, a former Apple engineer who jumped to Tesla in 2013 and eventually oversaw production of the Tesla Model 3, is back at Apple, where he's working with the team in charge of Apple's self-driving-car program.

Field rejoined Bob Mansfield, who is leading Apple's Project Titan, the tech journalist John Gruber and Reuters reported late Thursday night.

Field stepped away from Tesla in May. The electric-car maker officially announced his departure in July.

Project Titan has shown signs of life in recent weeks, despite earlier rumors that the division was flailing.

Doug Field, a former Apple engineering executive who recently oversaw production of Tesla's Model 3 sedan, has returned to Apple to work with Bob Mansfield, who is leading Apple's self-driving-car program, Project Titan.

Field worked in Apple's Mac division in 2013 before going to Tesla. He stepped away from the electric-car maker in May, and Tesla officially announced his departure in July.

The tech correspondent John Gruber and Reuters reported Field's new role at Apple late Thursday night.

Revelations about Project Titan that emerged last month hinted that the program was apparently more robust than previously thought. According to an affidavit filed in an FBI investigation, Apple has been working on components that could be used in some type of vehicle.

Apple was also building prototypes and had requirements for power, battery system, and "drivetrain suspension mounts," according to the affidavit.

Perhaps the biggest hint was that some 5,000 employees were given access to information about "the Project," as it's described in the affidavit. Previous estimates pegged the number at about 1,000.